This invention relates to an IC card which is used as a cash card or a credit card issued by a financial institution, such as a bank.
The present time has been called a cashless era, and goods can be purchased without using cash, simply by utilizing cards issued by credit card companies or the like. Plastic cards, embossed cards, magnetic stripes cards, etc. are usually used as cash or credit cards. These cards, however, have structures which can be easily forged, and their improper use is a significant problem. To solve this problem, an information card has recently been developed, which is commonly termed an IC card, in which an IC circuit with a secret key number, etc. stored therein is assembled such that the secret key number can not be readily externally read out. This IC card is difficult to forge and thus has excellent security, and it can also store a large quantity of information.
The IC card as noted above is delivered to a customer via an IC card manufacturing stage, an IC card issuing stage, and a personal information number (PIN) registration stage. After manufacture, the IC card is sent by mail or the like. Therefore, in the event of the IC card being stolen in transit, it is then possible to carry out a fraudulent transaction, using a real IC card rather than a forged one. For example, when the IC card is stolen between the manufacturing step and issuing step, it may be used by falsely writing data which is usually written subsequent to the card being issued.
Meanwhile, even after an IC card has been delivered to a customer through a regular route, the following inconvenience will occur.
The important data, such as the PIN noted above, is stored in a data memory, consisting, for instance, of an EP-ROM provided in the IC card. Since the IC card is carried by the customer in various ways, it is likely that data stored in the data memory might be altered by the influence of static electricity and ultraviolet rays. In such a case, however, there is no means for detecting any occurrence of alteration of data due to an abnormality in the memory, so that a transaction involving use of the IC card may possibly be effected with erroneous data.